def add_two_numbers(a,b):
    return a+b
print(add_two_numbers(1,2))
def is_prime(n):
    if n<=1: return False
    for i in range(2,n):
        if n%i==0: return False
    return True
print(is_prime(7))
#递归实现阶乘
def factorial(n):
    if n==0:
        return 1
    else:
        return n*factorial(n-1)
    print(factorial(5))